Nuclear Mean Field Research Articles

Application of the Gaussian expansion method to Hartree-Fock calculations(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Application of the Gaussian expansion method to Hartree-Fock calculations(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Description of the single-particle motions around two inert cores(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Description of the single-particle motions around two inert cores(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Ground and single-particle properties from Gogny+Tensor mean-field calculations(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Ground and single-particle properties from Gogny+Tensor mean-field calculations(Poster presentation,YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Opening Address(YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Opening Address(YITP Workshop on New Developments in Nuclear Self-Consistent Mean-Field Theories (MF05))

Sensitive behavior of [formula omitted]-decay amplitude within QRPA and broken [formula omitted] symmetry in nuclei

Making use of an identity transformation independent of a nuclear model, we represent the 2 ν β β -amplitude as a sum of two terms. One term accounts for most of the sensitivity of the original 2 ν β β -amplitude to g p p ′ for realistic g p p ′ ≃ 1 (with g p p ′ being the ratio of the triplet and singlet p– p interaction strengths) and is determined by a specific energy-weighted sum rule. The sum rule depends only on the particle–particle residual interaction (being linear function of g p p ′ in the QRPA) and passes through zero at the point g p p ′ = 1 where the Wigner SU ( 4 ) symmetry is restored in the p– p sector of the Hamiltonian. The second term in the decomposition of the 2 ν β β -amplitude is demonstrated within the QRPA to be a much smoother function for the realistic values of g p p ′ than the original 2 ν β β -amplitude. This term is mainly determined by the intensity of the spin–orbit interaction of the nuclear mean field. Thus, the analysis of the present work reveals the reasons for the sensitivity of the 2 ν β β -amplitude to different components of the nuclear Hamiltonian and thereby can help in constraining nuclear model uncertainties in calculations of the amplitude.

Effects of isospin and energy dependences of the nuclear mean field in spallation reactions

In many applications of the intranuclear-cascade (INC) model to spallation reactions, all nucleons in the target are assumed to move in a common potential well. However, the potential depth should depend upon nucleon isospin and energy. The present paper describes the first results obtained after the introduction of these features in the Liege INCL3 model. It is shown that such modifications change cascade particle multiplicities significantly but total particle multiplicities are only slightly altered. Nucleon inclusive cross-sections are not modified significantly, except in the region of the quasi-elastic peaks. In particular, the centroid of the peak in neutron double differential cross-sections relative to proton-induced reactions can be sizeably shifted toward larger energy losses, as is observed experimentally. Implications of these results are discussed.

Charge- and parity-projected Hartree–Fock study with the tensor force of light nuclei

We propose a mean field framework in which the charge and the parity symmetries of a single-particle state are broken. We break these symmetries to incorporate the correlation induced by the tensor force into a nuclear mean field model. We perform the charge- and the parity projections before variation and obtain a Hartree-Fock-like equation (charge- and parity-projected Hartree-Fock equation), which is solved self-consistently. We apply the Hartree-Fock-like equation to the alpha particle and find that, by breaking the parity and the charge symmetries, the correlation induced by the tensor force is obtained.

Shell-model description of monopole shift in neutron-rich Cu

Variations in the nuclear mean-field, in neutron-rich nuclei, are investigated within the framework of the nuclear shell model. The change is identified to originate mainly from the monopole part of the effective two-body proton-neutron interaction. Applications for the low-lying states in odd-$A$ Cu nuclei are presented. We compare the results using both schematic and realistic forces. We also compare the monopole shifts with the results obtained from large-scale shell-model calculations, using the same realistic interaction, in order to study two-body correlations beyond the proton mean-field variations.

Momentum distributions of projectile spectators: a new tool to investigate the equation of state of nuclear matter

High resolution measurements with a magnetic spectrometer show a post-acceleration of the projectile-like residues produced in relativistic heavy-ion collisions. The observed post-acceleration increases with the mass loss of the residual fragments. Lighter residues are observed to be produced at velocities even higher than the projectile. A dependence with the mass of the target and the energy of beam is also observed. This effect is interpreted as the response of the projectile spectator to the participant blast indicating a momentum dependence of the nuclear mean field.

Momentum distributions of projectile spectators: a new tool to investigate the equation of state of nuclear matter

High resolution measurements with a magnetic spectrometer show a post-acceleration of the projectile-like residues produced in relativistic heavy-ion collisions. The observed post-acceleration increases with the mass loss of the residual fragments. Lighter residues are observed to be produced at velocities even higher than the projectile. A dependence with the mass of the target and the energy of beam is also observed. This effect is interpreted as the response of the projectile spectator to the participant blast indicating a momentum dependence of the nuclear mean field.

Solution of the Skyrme–Hartree–Fock–Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (IV) HFODD (v2.08i): a new version of the program

We describe the new version (v2.07f) of the code HFODD which solves the nuclear Skyrme-Hartree-Fock or Skyrme-Hartree-Fock-Bogolyubov problem by using the Cartesian deformed harmonic-oscillator basis. In the new version, all symmetries can be broken, which allows for calculations with angular frequency and angular momentum tilted with respect to the mass distribution. The new version contains an interface to the LAPACK subroutine ZHPEVX.

SEMICLASSICAL ORIGIN OF SHELL STRUCTURES IN DEFORMED NUCLEI: DEPENDENCE ON SURFACE DIFFUSENESS AND EFFECT OF SPIN-ORBIT COUPLINGS

Shell structures in nuclear mean field potentials are analyzed using semiclassical periodic-orbit theory. rα-type potential model is taken as an approximation of Woods-Saxon model, and spin-orbit coupling is also taken into account. Using this model, we examine shell structure as functions of deformation, nuclear size (diffuseness), and spin-orbit coupling strength. Significant roles of periodic orbit bifurcations for strong deformed shell effects are clarified. Special attentions will be paid to bifurcations of the 'bridge orbits', which emerge from symmetric orbits and then submerge in other symmetric orbits by varying a potential parameter.

Transport properties of isospin effective mass splitting

We investigate in detail the momentum dependence (MD) of the effective in medium nucleon–nucleon (NN) interaction in the isovector channel. We focus the discussion on transport properties of the expected neutron–proton (n/p) effective mass splitting at high isospin density. We look at observable effects from collective flows in heavy ion collisions (HIC) of charge asymmetric nuclei at intermediate energies. Using microscopic kinetic equation simulations nucleon transverse and elliptic collective flows in Au+Au collisions are evaluated. In spite of the reduced charge asymmetry of the interacting system interesting isospin-MD effects are revealed. Good observables, particularly sensitive to the n/p mass splitting, appear to be the differences between neutron and proton flows. The importance of more exclusive measurements, with a selection of different bins of the transverse momenta ( p t ) of the emitted particles, is stressed. In more inclusive data a compensation can be expected from different p t -contributions, due to the microscopic isospin-MD structure of the nuclear mean field in asymmetric matter.

Nuclear mean field from chirally symmetric effective theory

The mean-field theory of the nuclear many-body problem proposed recently by Furnstahl, Serot, and Tang (FST) is discussed. The FST chiral Lagrangian is derived in terms of an effective field theory. This new approach allows one to construct in a controlled manner the universal nuclear Lagrangian consistent with symmetries of QCD. The FST Lagrangian is constructed by using power counting, i.e., the expansion in powers of the lowest lying hadronic fields and their derivatives. Terms in the Lagrangian are organized by applying Georgi’s naive dimensional analysis and “naturalness” condition. The relevant degrees of freedom are nucleons, pions, an isoscalar-vector field ω meson), an isoscalar-scalar field (σ meson), and an isovector-vector field (ρ meson). The chiral symmetry is realized nonlinearly using a standard WCCWZ procedure.

Experimental indications for the response of the spectators to the participant blast.

Precise momentum distributions of identified projectile fragments, formed in the reactions 238U+Pb and 238U+Ti at 1A GeV, are measured with a high-resolution magnetic spectrometer. With increasing mass loss, the velocities first decrease as expected from previously established systematics, then level off, and finally increase again. Light fragments are on the average even faster than the projectiles. This finding is interpreted as the response of the spectators to the participant blast. The reacceleration of projectile spectators is sensitive to the nuclear mean field and provides a new tool for investigating the equation of state of nuclear matter.

Semimicroscopical description of the simplest photonuclear reactions accompanied by excitation of the giant dipole resonance in medium-heavy mass nuclei

A semimicroscopical approach is applied to describe photoabsorption and partial photonucleon reactions accompanied by the excitation of the giant dipole resonance (GDR). The approach is based on the continuum-RPA (CRPA) with a phenomenological description for the spreading effect. The phenomenological isoscalar part of the nuclear mean field, momentum-independent Landau-Migdal particle-hole interaction, and separable momentum-dependent forces are used as input quantities for the CRPA calculations. The experimental photoabsorption and partial $(n,\gamma)$-reaction cross sections in the vicinity of the GDR are satisfactorily described for $^{89}$Y, $^{140}$Ce and $^{208}$Pb target nuclei. The total direct-neutron-decay branching ratio for the GDR in $^{48}$Ca and $^{208}$Pb is also evaluated.

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.

In-medium baryon interactions and hypernuclear structure

We introduce a microscopic and relativistic theory describing free scattering and finite nuclei for the octet baryons in a consistent quantum field theoretical framework based on Dirac–Brueckner theory and nuclear mean field. In a first quantitative approach, yet still heuristic for dealing with the Λ hyperon, the quality of the description of finite (hyper)nuclei based on free meson exchange potentials is competitive with those from purely phenomenological relativistic mean-field calculations. In contrast to the latter our approach has the advantage of having a microscopic link to free interactions and complete control of which classes of diagrams are included. As a complementary way for determining hyperon–hyperon and hyperon–nucleon interactions the use of Hanbury–Brown–Twiss interferometry is discussed.

Elliptic flow in intermediate energy heavy ion collisions and in-medium effects

We investigate elliptic flow in heavy ion collisions at intermediate energies. In doing this, we implement and use a lattice-Hamiltonian model of the nuclear interaction and we also study the effect of in-medium nucleon-nucleon cross sections that follow consistently from the momentum-dependence of the nuclear mean field.

Interplay of three-body interactions in the EOS of nuclear matter

The equation of state of symmetric nuclear matter has been investigated within Brueckner approach adopting the charge-dependent Argonne V 18 two-body force plus a microscopic three-body force based on a meson-exchange model. The effects on the equation of state of the individual processes giving rise to the three-body force are explored up to high baryonic density. It is found that the major role is played by the competition between the strongly repulsive ( σ, ω)-exchange term with virtual nucleon–antinucleon excitation and the large attractive contribution due to ( σ, ω) exchange with N ∗(1440) resonance excitation. The net result is a repulsive term which shifts the saturation density corresponding to the only two-body force much closer to the empirical value, while keeping constant the saturation energy per particle. The contribution from ( π, ρ)-exchange 3BF is shown to be attractive and rather small. The analysis of the separate three-body force contributions allows to make a comparison with the prediction of Dirac–Brueckner approach which is supposed to incorporate via the dressed Dirac spinors the same virtual nucleon–antinucleon excitations as in the present three-body force. The numerical results suggest that the three-body force components missing from the Dirac–Brueckner approach are not negligible, especially at high density. The calculation of the nuclear mean field and the effective mass shows that the three-body force affects to a limited extent such properties.